On the contrary恰恰相反 The book is not easy. On the contrary, it is rather difficult. It wasn't a good thing; on the contrary it was a huge mistake.
Once一旦 Once a beginning is made, the work is half done. Once you begin, you must continue.
Otherwise否则 Do what you have been told; otherwise you will be punished. You'd better go now, otherwise you'll miss the train.
Provided 如果… I will come provided I have time. Provided it's fine we will have a pleasant holiday. Scarcely…when(hardly…when)一…就(句子经常要倒装) Scarcely had he gone out when it began to rain. I had hardly arrived the platform when the train left
When 1) 当,当…之后 I will be there waiting for you when you arrive. I started my elementary school when I was 6. 2) 就在那个是时候 (常表示两个动作几乎同时发生或者when引导的动作在主句的动作发生之时) I was leaving the house when someone knocked at my door. It was on my way home when I met my classmate. 3) 既然 I can’t tell you anything when you won’t listen. We need to adjust the prices of our products when prices of raw materials rise so sharply. 4) 虽然 I lose temper when I shouldn’t.
While 当…时期 Please don’t talk so loud while people are reading. 1) 而 You clean the window while I sweep the floor. 2) 虽然 While I like the color of it, I don’t like this shape.